Oh well if we're going that way, isn't it unfair that kata can't move during her ult, gets interrupted by stun and doesn't knock up opponents?
Wukongs ult is fine and would honestly only be kinda overpowered if it benefits from lifestealing effects.

Katarina does not benefit from lifesteal with her her AD / AP ratio abilities. She benefits form spell vamp yes. As do you, but why would you get that right? You can move around freely. Katarina has to be stationary.

yeah. Wukong's Ult - Cyclone doesn't benefit from lifesteal but it does benefit from spell vamp. Tried it first on custom before making my own guide.
Check out my guide on mobafire named "Wukong the Clash King". They do criticize Gunblade on Wukong but it's effective.